Telecommunications system and method

ABSTRACT

A mobile communications session is provided to a mobile node using an internet protocol. A home packet data network communicates with an affiliated mobile node. The home packet data network includes a home agent of the mobile node. A visited packet data network communicates with an affiliated mobile node. A packet data gateway controls the communication between the home and visited packet data networks. Following a change of affiliation from the home packet data network to the visited packet data network, the packet data gateway and the home agent establish a route to the mobile node via the packet data gateway, which controls communication between the home packet data network and the mobile node affiliated with the visited packet data network. If the mobile node roams between a 3GPP network and a non-3GPP network; the packet data gateway controls communication, using resources on the 3GPP network by the mobile node.

FIELD OF THE INVENTION

The present invention relates to telecommunications systems operable toprovide mobile communications sessions to mobile nodes using an internetprotocol, in which the mobile nodes change affiliation from a homepacket data network to a visited packet data network.

The present invention also relates to methods for providing mobilecommunications sessions to mobile nodes using an internet protocol, whenthe mobile node changes affiliation from a home packet data network to avisited packet data network.

BACKGROUND OF THE INVENTION

Packet data networks provide a facility for communicating data in theform of internet packets to and from communicating devices or nodes. Thepacket data network may provide a facility for mobile communicationswith a node (referred to generally as a mobile node) using, for examplea radio access interface, which allows the communicating device node tobe mobile within a radio coverage area provided by the network. Forexample, the General Packet Radio Service (GPRS) is a telecommunicationsstandard developed by the 3rd Generation Project Partnership (3GPP)which provides a facility for communicating internet packets via a radioaccess interface. A GPRS network can be formed using a Global System forMobiles (GSM) or a Universal Mobile Telecommunications System (UMTS)backbone network. GPRS provides support for packet-orientated servicesand attempts to optimise network and radio resources for packet datacommunications using the Internet Protocol (IP).

The Internet Engineering Task Force (IETF) is a body, which isresponsible for developing internet protocols for facilitatingcommunications via the internet. For example, a well establishedinternet protocol is the internet protocol version 4 (IPV4) which hasbeen developed and standardised for personal computers to access theinternet. The IETF has also developed a further standard known as theinternet protocol version 6 (IPV6) which provides an improvement withrespect to the IPV4 in terms of facilitating mobile communications andincreased addressing options for user equipment. Both IPv4 and IPv6provide a facility in which a mobile node can roam from the mobilenode's home network to a visited network and support an internetprotocol communications session.

SUMMARY OF INVENTION

According to an aspect of the present invention there is provided atelecommunications system operable to provide a mobile communicationssession to a mobile node using an internet protocol. Thetelecommunications system comprises a home packet data network and avisited packet data network. The home packet data network is operable tocommunicate internet packets to and from the mobile node to provide thecommunications session, when the mobile node is affiliated with the homepacket data network. The home packet data network includes a home agentof the mobile node. The visited packet data network is operable tocommunicate internet packets to and from the mobile node to provide thecommunications session, when the mobile node is affiliated with thevisited packet data network. One of the home packet data network or thevisited packet data network includes a packet data gateway forcontrolling the communication of the internet packets to and from thehome packet data network from and to the visited packet data network.Upon receipt of a binding update internet packet providing a care ofaddress of the mobile node following a change of affiliation from thehome packet data network to the visited packet data network, the packetdata gateway and the home agent are operable to establish a route forthe internet packets between the home agent and the mobile node via thepacket data gateway. The packet data gateway can therefore control thecommunication of the internet packets from the home packet data networkto the mobile node and the communication of the internet packetsreceived from the mobile node via the visited packet data network whenthe mobile node is affiliated with the visited packet data network.

Embodiments of the present invention provide a facility for allowingcontrol of resources of a packet data network by a mobile node after themobile node has roamed from the mobile node's home packet data networkto a visited packet data network. Control of communications resources isprovided using a packet data gateway. By detecting a binding updatepacket communicated by the mobile node following a change of affiliationfrom the mobile node's home packet data network to a visited packet datanetwork providing a care of address within the visited network, a homeagent within the home network is arranged to communicate internetprotocol packets addressed to the mobile node at the care of address inthe visited network via the packet data gateway. The packet data gatewayis also arrange to communicate the internet packets addressed to themobile node at the care of address to the mobile node within the visitednetwork. The packet data gateway can thereby control the use ofresources on the home packet data network or the visited packet datanetwork.

Embodiments of the present invention therefore provide an arrangement inwhich internet packets which are communicated to and from a mobile nodewhich has roamed from its home network to a visited network are routedthrough a packet data gateway. As such control of the internet packetsto or from the mobile node can be effected by the packet data gateway.The packet data gateway may provide policing functions as well asbilling, authentication, authorisation and administration. In oneexample the packet data gateway forms part of the home network of themobile node although in other examples the packet data gateway formspart of a network to which the mobile node has roamed which will bereferred to as the visited network.

In examples where the packet data gateway forms part of the homenetwork, a security internet protocol tunnel may be established betweenthe packet data gateway and the mobile node in the visited network. Thesecurity internet protocol tunnel may in some embodiments be an IPsectunnel, in accordance with the 3GPP standard.

3GPP has provided a requirement for internet packets ingressing to andegressing from a packet data network to be routed via a packet datagateway to control the communication of internet packets, which mayinclude controlling communications resources. However, mobile internetprotocol standards, such as IPv4 and IPv6, when used to provide a careof address to a roaming mobile node, could result in a packet datagateway of a packet data network either not recognising a receivedinternet protocol packet, which is to be communicated to the mobilenode's home agent within the packet data network, or could result in aninternet packet reaching the home agent of the mobile node or beingcommunicated to the mobile node from the home agent without passingthrough the packet data gateway. By detecting a binding update internetpacket which is sent by the mobile node with its care of address withinthe visited network and adapting the home agent and the packet datagateway to route the internet packets via the packet data gateway, thepacket data gateway can be arranged to control the communication ofinternet packets for a mobile node. As a result, if the mobile noderoams from for example a 3GPP network to a non-3GPP network or to a 3GPPnetwork from a non-3GPP network, the packet data gateway is able tocontrol the communication of internet packets, using resources on the3GPP network by the mobile node.

Various further aspects and features of the present inventions aredefined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying drawings where likeparts are provided with corresponding reference numerals and in which:

FIG. 1 provides a schematic block diagram illustrating an example inwhich a mobile node roams from a 3GPP packet data network to a non-3GPPpacket data network;

FIG. 2 provides a schematic block diagram for an example correspondingto the shown in FIG. 1, in which the mobile node generates a co-locatedcare of address and the packet data gateway is in the home packet datanetwork, and illustrating an example of the present technique;

FIG. 3 provides a schematic block diagram for the example shown in FIG.2, with the packet data gateway and the home agent arranged to tunneldata between each other;

FIG. 4 provides a schematic block diagram for an example correspondingto the shown in FIG. 1, in which the visited network includes a foreignagent and the packet data gateway is in the home packet data network,and illustrating an example of the present technique;

FIG. 5 provides a schematic block diagram for the example shown in FIG.4, with the packet data gateway and the home agent being co-located inaccordance with another example of the present technique;

FIG. 6 provides a schematic block diagram of a home packet data networkand a visited packet data network, in which the visited network includesa packet data gateway and a foreign agent, and illustrating an exampleof the present technique;

FIG. 7 provides a schematic block diagram of a home packet data networkand a visited packet data network, in which the visited network includesa packet data gateway and a foreign agent, and illustrating an exampleof the present technique in which the packet data gateway and theforeign agent tunnel data packets there between;

FIG. 8 a provides a schematic block diagram for an example in which thepacket data gateway is located in the visited packet data network andthe mobile node generates a co-located care of address illustrating anexample of the present technique; FIG. 8 b shows the same example asFIG. 8 a except that the foreign agent is co-located with the packetdata gateway;

FIG. 9 provides a schematic block diagram for an example correspondingto the shown in FIG. 1, in which the mobile node operates in accordancewith internet protocol version 6 (IPv6), the packet data gateway is inthe home packet data network, and illustrating home agent tunnelingaccording to the present technique;

FIG. 10 provides a schematic block diagram for the example of FIG. 9,illustrating a route optimisation process through a correspondent nodebinding update process;

FIG. 11 provides a schematic block diagram for an example in which themobile node operates in accordance with internet protocol version 6(IPv6), the packet data gateway is in the visited packet data network,and illustrating home agent tunneling according to the presenttechnique; and

FIG. 12 provides a schematic block diagram for the example of FIG. 11,illustrating a route optimisation process through a correspondent nodebinding update process.

DESCRIPTION OF EXAMPLE EMBODIMENTS

3GPP and Non-3GPP Networks

As will be appreciated, embodiments of the present invention findapplication with various types of packet data networks. However, in oneexample either a home network of a mobile node or a visited network ofthe mobile node is arranged to operate in accordance with a 3GPPstandard, or both whilst in other embodiments one of the home network orthe visited network may operate in accordance with a standard which is anormal 3GPP standard.

FIG. 1 shows an example in which a mobile node MN roams from a homenetwork HN to a visited network VN. As shown in FIG. 1 the home networkHN is a packet data network which operates in accordance with a GeneralPacket Radio System (GPRS) and so elements forming part of the GPRSnetwork correspond to the GPRS standard. The GPRS network thereforeincludes a GPRS Gateway Support Node (GGSN) 1, a Serving Gateway SupportNode (SGSN) 2, and a Radio Network Controller (RNC) 4. Connected to theRNC 4 is shown two Node Bs 6, 8 which serve to provide a radio accessinterface to mobile nodes within a radio coverage area provided by eachof the Node Bs. It will of course be appreciated that within a GPRSnetwork there are likely to be many RNCs and Node Bs, although only oneRNC 4 and two Node Bs 6, 8 are shown in FIG. 1 for simplicity.

As shown in FIG. 1, the mobile node MN when attached to the home networkcommunicates via the radio access interface in accordance with theUniversal Terrestrial Radio-Access Network (UTRAN) standard to transmitand receive data. The data transmitted and received between the Node Bs6, 8 and the mobile node MN represents internet protocol packets. Thusin accordance with an example embodiment a communications service isprovided to the mobile node MN which establishes a communicationssession between the mobile node MN and the home network HN in whichinternet packets are transmitted to and received from the Node Bs 6, 8via the radio access network. Whilst the mobile node MN is attached tothe home network, the internet packets are communicated to and from ahome agent HA 10 which is connected to the GGSN 1. If the mobile node MNstays affiliated with the home network HN then the internet protocolpackets which are communicated with a correspondent node CN are routedvia the home agent 10.

According to an example embodiment the mobile node MN may roam toanother network. The mobile node MN becomes attached to a visitednetwork VN having left a radio coverage area provided by the homenetwork HN. Thus as represented by an arrow 12 in FIG. 1 the mobile nodeMN roams from the home network HN to the visited network VN.

In accordance with known internet protocol standards, when a mobile noderoams to a visited network VN then the mobile node will execute abinding update so that the home agent 10 can forward internet packets tothe mobile node MN in the visited network VN. This is true for bothinternet protocol version 4 (IPv4) and internet protocol version 6(IPv6). Thus as those acquainted with the internet protocols willappreciate, once the mobile node has roamed to a visited network abinding update procedure is followed as a result of which the mobilenode acquires a care of address which is to be used for communicatingpackets sent to and received from the mobile node whilst it isaffiliated with the visited network. In addition when a mobile noderoams to a visited network which is operating in accordance with IPv6,then in accordance with a route optimisation procedure a correspondentnode is informed of the mobile node's care of address within the visitednetwork and a correspondent node binding update process is performed.

Typically the visited network will include a Wireless Access Gateway WAG14, via which all internet packets transmitted from the foreign network(egressing) or received by the visited network (ingressing) will pass.

In order to allow for a GPRS network to monitor the use of resources ofthe GPRS network and to administer authentication, billing and policingof the communication of internet packets on the GPRS network, a packetdata gateway (PDG) 16 is provided. Thus as shown in FIG. 1 a packet datagateway PDG 16 is attached to home agent 10. However, in order tocorrectly apply policing, resources and billing and other administrativefunctions all internet packets egressing from the home network andingressing to the home network must pass through the packet data gateway(PDG) 16. However, once the mobile node MN has roamed to a visitednetwork VN and acquired a care of address the internet packets sent fromMN or received by the MN will in accordance with an IPv4 operationsimply be routed to the home agent 10 and not pass through the packetdata gateway.

According to the present technique internet packets which are sent by orreceived from a mobile node MN which has roamed to a visited network topass through a packet data gateway. The packet data gateway may be ineither the home network as it is shown in FIG. 1 or may be in thevisited network. Further example embodiments will be explained below forboth the IPv4 case, the IPv6 case and other scenarios in which the PDGis either in the home network or the visited network or indeed whetherthe visited network includes a foreign agent or not. These embodimentsarrange for internet packets sent to and received from the mobile nodewhen it has roamed to a visited network to be routed via a packet datagateway. These example embodiments will now be explained.

PDG in the Home Network with IPv4 and No Foreign Agent

FIG. 2 shows an example where the packet data gateway is present withina home network HN of a mobile node MN. Thus as shown in FIG. 2 anexample where the home network HN and visited network VN correspondingto those shown in FIG. 1 are represented in a simplified form. Theexample shown in FIG. 2 shows the packet data gateway PDG 16.1 withinthe home network HN with the mobile node MN having roamed to the visitednetwork VN.

In accordance with a conventional operation, once the mobile node MN hasroamed to the visited network VN a binding update procedure isperformed. For the example shown in FIG. 2 the Internet protocol versionis 4 (IPv4) so that the mobile node MN performs a binding updateprocedure in accordance with the IPv4 standard. Furthermore, for theexample shown in FIG. 2, the visited network VN does not include aforeign agent so that the mobile node operates to generate its own careof address which is referred to as a co-located care of address CLCOA.Thus in accordance with the binding update procedure, a binding updatepacket 20 is communicated to the home agent 10 in the home network HN.However, since all internet protocol packets entering and leaving thehome network HN must be routed through the packet data gateway 16.1 thebinding update 20 is tunneled through the PDG. Accordingly, anencapsulated internet protocol packet 22 sent between the mobile MN andthe PDG 22 has an additional header with a destination address 22.1being that of the PDG 16, the source address 22.2 being the colocatedcare of address CLCoA of the MN and the payload providing the bindingupdate packet 20. Once the tunneled packet 22 is received by the PDG 16the additional tunneling header addresses 22.1, 22.2 are removed and thepacket is forwarded by the PDG to the home agent 10.1.

In accordance with this example, the home agent 10.1 is adapted toensure that any internet packets which are addressed to the mobile nodeMN in the visited network at the care of address CLCoA are routed viathe packet data gateway 16.1. In the present example shown in FIG. 2 therouting of the packets to the packet data gateway 16.1 by the home agent10.1 for the mobile node MN at the co-located care of address CLCoA isarranged by updating a routing table 24 which forms part of the homeagent 10.1. Thus in the routing table the home agent 10.1 includes thehome address of the mobile node HA in association with the co-locatedcare of address CLCoA. In addition, in association with the co-locatedcare of address CLCoA, a default router option is set to force thepackets received by the home agent 10.1 for the mobile node MN at theco-located care of address CLCoA to be routed through the packet datagateway 16.1. FIG. 3 which will be explained shortly, provides anexample in which internet packets for the mobile node in the visitednetwork are tunneled to the packet data gateway 16.1 from the home agentfor communicating to the mobile node MN.

Returning to FIG. 2, an internet packet 26 sent from a correspondentnode CN to the mobile node MN is routed to the home agent 10.1. Therouting table 24 has been updated and so the internet packet, addressedto the co-located care of address CLCoA of the mobile MN is forwarded tothe packet data gateway 16.1 as the internet packet 28. Thus theinternet packet 28 includes the co-located care of address CLCoA 28.1 asthe destination address, the address of the home agent 10.1 as thesource address 28.2 and the data for communication to the mobile node28.3. At the packet data gateway 16.1 the received internet packet 28 istunneled to the mobile node using a mobile internet protocol tunnel 32set up between the packet data gateway and the mobile node MN. Thus byapplying the co-located care of address CLCoA as the destination address30.1 and the address of the PDG as the source address 30.2 the data canbe communicated via the mobile IP tunnel 32 to the mobile node MN in thevisited network VN.

In order to provide a secure communication of the internet packet to themobile node MN within the visited network a secure internet protocoltunnel 34 is established within the mobile IP tunnel 32. Thus as shownby the form of the internet packet 30 which is to be sent to the mobilenode MN an additional header 36 is included which has a source addressand a destination address. In one example the secure internet protocoltunnel conforms to the IPsec standard. Thus the communication of thetunneled internet packet between the packet data gateway 16.1 and themobile node MN conforms to the 3GPP standard.

As shown in FIG. 2, the destination address 36.1 is the end of the IPsectunnel 34 and so includes the destination address of the IPsec MN 36.1.The source address is then the start of the IPsec tunnel which isdesignated as the IPsec PDG 36.2. Thus as shown in FIG. 2, the IPsecheader 36 is added at the packet data gateway 16.1 and communicated tothe mobile node MN within the IPsec tunnel 34. The mobile node receivesthe IPsec encapsulated internet packet removes the IPsec header 36 andthen receives the internet packet 28 at the co-located care of addressCLCoA. Returning to FIG. 3, an example is illustrated which correspondsto that shown in FIG. 2. However, in contrast to FIG. 2 instead ofupdating the routing tables 24 of the home agent 10.1, an internetprotocol tunnel is set up between the home agent 10.1 and the packetdata gateway 16.1 which is represented in FIG. 3 as a tunnel 40. Thus asshown the received packet which is addressed to the mobile node MN atthe co-located care of address CLCoA 42 is encapsulated as a tunneledpacket by adding a header 44. The header 44 includes a destinationaddress 44.1 which is that of the packet data gateway 16.1 and a sourceaddress 44.2 which is that of the home agent 10.1.

After the packet 42 has been received by the packet data gateway 16.1then communication of the packet 42 to the mobile node corresponds tothe same process as represented in FIG. 2.

PDG in Home Network Mobile IPv4 Visited Network Includes a Foreign Agent

FIG. 4 provides an illustration of a scenario which corresponds to thatof the examples shown in FIGS. 2 and 3, that is with packet data gatewayin the home network HN and with the internet packets being communicatedin accordance with IPv4. However, in FIG. 4 the visited network VNincludes a foreign agent FA 60 which acts as if it were a home agent inthe visited network VN to the mobile node MN and performs the functionsof the home agent for the mobile node MN in the visited network VN. Thusin accordance with the IPv4 standard the foreign agent 60 generates acare of address of the mobile node and initiates the binding updateprocess. Thus in accordance with a binding update procedure a bindingupdate packet 62 is sent via a binding update tunnel 64 between theforeign agent 60 and the packet data gateway 16.2. After the bindingupdate packet 62 has been received by the packet data gateway 16.2 it isforwarded by the packet data gateway 16.2 to the home agent 10.2.

The operation of the scenario shown in FIG. 4 corresponds to that of theoperation shown in FIGS. 2 and 3 with the home agent 16.2 eitherupdating its routing table or tunneling packets which are to be routedto the mobile node MN in a visited network VN at the care of addressCOA, via the packet data gateway. Thus as for FIG. 2 the home agent 16.2could update its routing table to route received packets to the mobilenode MN via the packet data gateway or could establish a tunnel toencapsulate the packets to be sent to the mobile node MN by adding aheader 66 with a destination address 66.1 of the packet data gateway asource address 66.2 of the home agent 10.2.

The presence of the foreign agent 60 in scenario shown in FIG. 4 adds anadditional complication because an internet protocol security tunnel 68must start at the packet data gateway 16.2 and end at the mobile nodeMN. However, because the internet protocol security tunnel (IPsec) mustbe secure then it is not possible for a tunnel to be established withinthe IPsec tunnel. However, in order to communicate internet packets tothe mobile node MN within the visited network VN for the arrangementshown in FIG. 4, a mobile internet protocol tunnel is establishedbetween the packet data gateway 16.2 and the foreign agent 60 in orderfor the internet packets to reach the mobile node MN. To address thisproblem according to the embodiment shown in FIG. 4 the packet datagateway 16.2 is arranged to set up a mobile EP tunnel 68 before settingup the EP spec tunnel 71 which comprises a tunnel 71.1 between thepacket data gateway 16.2 and the foreign agent 60 and a part 70.2between the foreign agent 60 and the mobile node MN. To this end thepacket data gateway 16.2 encapsulates the packet to be forwarded to themobile node with a header having the destination address as the foreignagent with the source address as the packet data gateway. The packetdata gateway 16.2 then inserts an IPsec header 70 with a source address70.1 being that of the packet data gateway (IPsec PDG) and thedestination address being that of the mobile node (IPsec MN) and insertsthe IPsec header 70 between the mobile internet protocol tunnel headeradded by the packet data gateway to form an encapsulated packet 73.

FIG. 4 illustrates a process for communicating the internet packet 67 tothe mobile node MN in the visited network VN: The home agent 16.2encapsulates the internet packet 67 to be communicated with a header 66having the destination address 66.1 as the packet data gateway 16.2 andthe home agent HA as the source address 66.2. Once the packet 66 to becommunicated to the mobile node MN has been received at the packet datagateway 16.2 the packet which is addressed to the mobile node at thecare of address 67 is encapsulated with a mobile IP header 70 which hasthe foreign agent as the destination address 70.1 and the packet datagateway as the source address 70.2. However, the packet data gatewayalso inserts an IPsec header 72 having the destination address of the MN72.1 as the end of the IPsec tunnel and the address of the packet datagateway IPsec PDG as the source address 72.2.

Since the mobile IP tunnel 68 terminates at the foreign agent 60 themobile IP header 70 is removed and the packet is then forwarded to amobile node which is the end of the IPsec tunnel 70.2 as a result ofrouting using IPsec header 72. At the mobile node the IPsec header isremoved and the data packet is received at the mobile node at the careof address 67.1.

According to the arrangement shown in FIG. 4 the packet data gateway16.2 and the home agent 10.2 are arranged to communicate internetpackets to the mobile node MN via a foreign agent 60. An internetprotocol security tunnel (IPsec) has then been established between thepacket data gateway 16.2 and the mobile node MN even though the foreignagent exists in the visited network VN.

As an alternative solution FIG. 5 illustrates an example where thepacket data gateway is co-located with the home agent As a result thereis no requirement to adapt the routing table or establish a tunnelbetween the home agent the packet data gateway. However, the arrangementof the mobile IP tunnel being established before the IPsec tunnel asillustrated in FIG. 4 will also apply to FIG. 5.

PDG in Visited Network, IPv4 with a Foreign Agent in Visited Network

FIG. 6 provides an illustration of an example where the packet datagateway is provided within the visited network VN. As for the exampleshown in FIGS. 4 and 5 once the mobile node MN has roamed to the visitednetwork, the binding update process is performed in which a bindingupdate packet 80 is sent from the foreign agent 82 to a home agent 10.3within the home network HN. Thus as with the previous example theforeign agent 82 establishes a care of address for the mobile node MNand communicates a binding update packet to the home agent 10.3.However, as illustrated in FIG. 6 the foreign agent 82 is arranged tocommunicate the binding update packet to the home agent 10.3 via thepacket data gateway 16.3. For the example shown in FIG. 6 a routingtable 84 of the foreign agent 82 is adapted to identify the packet datagateway as the default next routing address for packets addressed to thehome agent 10.3 within the home network HN. In another example shown inFIG. 7 a foreign agent 82.1 is arranged to tunnel packets to the packetdata gateway 16.4 via a tunnel by encapsulating the packets forcommunication to the home agent using a tunneling header.

Returning to FIG. 6 the binding update packet 80 is communicated to thehome agent 10.3 via the mobile IP binding update tunnel 84. To this end,a mobile IP header 86 includes the home address of the mobile node HA asthe destination address 86.1 and the address of the packet-data gatewayPDG as the source address 86.2. Following receipt of the binding updatepacket 80 at the home agent 10.3 the home agent 10.3 updates informationthat the mobile node MN is at the care of address in the visited networkVN in accordance with a conventional IPv4 binding update. However, thehome agent 10.3 then operates to establish a mobile IP tunnel 87 betweenthe home agent 10.3 and the packet data gateway 16.3.

In this example the mobile internet protocol tunnel is required tocommunicate in the internet packet between the home agent and the packetdata gateway and between the packet data gateway and the foreign agent.Therefore the home agent 10.3 establishes statically or dynamically themobile IP tunnel 87 to tunnel a packet received at the home agent 10.3to the packet data gateway 16.3. An example of such a packet is shown tocarry an internet data packet from the correspondent node CN 88, whichhas the care of address of the mobile node CoA as the destinationaddress 88.1 and the mobile node's home address HA 88.2 as the sourceaddress. The internet data packet 88 received at the home agent 10.3 isthen tunneled via the mobile internet protocol tunnel 87 using themobile IP header 90. The mobile internet protocol header 90 includes theaddress of the packet data gateway as the destination address 90.1 andthe address of the home agent as the source address 90.2. The payload903 provides the received packet 88. Thus after the data packet 88 iscommunicated by the mobile internet protocol tunnel 87 and received atthe packet data gateway, the packet data gateway 16.3 removes the mobileinternet protocol header 90 to form a received data packet 88.

The packet data gateway 16.3 is then arranged to communicate thereceived packet 88 to the foreign agent 82 which is then forwarded tothe mobile node at the care of address 88.1. To this end, in one examplethe packet data gateway is arranged to identify the foreign agent as thedefault next address of data packets using an updated routing table 92.Alternatively, the care of address of the mobile node identifies theforeign agent.

Returning to FIG. 7 a corresponding example to that is shown in FIG. 6with the exception that the packet data gateway is arranged a tunnelpackets from the foreign agent 82.1. Thus the binding update procedureis the same as that shown in FIG. 6. However, unlike in FIG. 6 thereceived data packet 88 in step 3 is then encapsulated using a tunnelingheader 94 which has the destination address of the foreign agent as 94.1and the address of the packet data gateway as the source address 94.2.Thus the received packet 88 is recovered by removing the tunnelingheader 94 and forwarded by the foreign agent 82.1 to the mobile node MN.

PDG in Visited Network IPv4 with No Foreign Agent

FIG. 8 a illustrates an example in which packet data gateway 16.5 islocated within a visited network VN and communication is effected usingIPv4. For this example the mobile node MN generates its own co-locatedcare of address CLCoA as for the example illustrated in FIG. 2. Theexample shown in FIG. 8 a corresponds to that shown in FIG. 2 and soonly the differences between the example in FIG. 8 a and that in FIG. 2will be described. For the example shown in FIG. 8 a the packet datagateway 16.5 and home agent 10.5 are arranged to establish a bindingupdate tunnel 100 and a mobile internet protocol tunnel 102 as for theexample shown in FIG. 2. However, unlike the example shown in FIG. 2there is no requirement to establish an internet protocol securitytunnel between the home agent and the packet data gateway and likewisebetween the packet data gateway 16.5 and the mobile node MN. As for theexample shown in FIGS. 2 and 3 the mobile node MN is arranged to routeinternet packets to the home agent via the packet data gateway usingeither an update of a routing table or creating a tunnel. Otherwise theoperations for performing the binding update and communicating receiveddata packets 104 to the mobile node MN correspond to that explained inFIGS. 2 and 3 and supported by the other example embodiments in FIGS. 4,5, 6 and 7 and so these would not be described further.

PDG in Visited Network IPv4 with Foreign Agent Located in PDG

FIG. 8 b illustrates an example in which the foreign agent FA is locatedin the packet data gateway PDG 16.6. The PDG-FA combination is locatedwithin a visited network VN and communication is effected using IPv4.This is a simple scenario as packets do not have to be tunneled betweenthe foreign agent FA and the packet data gateway PDG in the visitednetwork, and no tunneling is required within the home network HN. Allthat is required, for both binding updates and packets arriving at thehome agent HA destined for the mobile node MN, is for two tunnels to beestablished between the home agent HA and the PDG-FA 16.6. These tunnelsare represented in FIG. 8 b in the same way as those shown in FIG. 8 a.

Mobile IPv6 Route Optimisation for Correspondent Node Binding Update

Example embodiments in which internet packets communicated to and from amobile node when attached to a visited network, so that these passthrough a packet data gateway for the mobile IPv6 case will now bedescribed with reference to FIGS. 9, 10, 11 and 12. FIGS. 9, 10, 11 and12 illustrate corresponding examples to those shown in FIGS. 2 to 8 forthe mobile IPv4 case. Generally, the mobile IPv6 case corresponds to theexamples for the mobile IPv4 except that for mobile IPv6 no foreignagent appears within the visited network because the mobile node isarranged to create its own care of address. However, unlike the mobileIPv4 case the mobile IPv6 case includes a procedure for routeoptimisation facilitated by a correspondent node binding updateprocedure. As such, further adaptation of the packet data gateway and/orthe home agent is required in order to arrange for all internet packetsto be routed to and from the mobile node within the visited network viaa packet data gateway.

Considering the example shown in FIG. 9, the mobile node which arrivesin the visited network VN and generates a binding update packet 200 forcommunication to its home agent 10.6 which is shown within the homenetwork HN. The binding update packet 200 includes a destination addressof its home agent within the home network 200.1 (which may be the mobilenode's own home address), a care of address CoA of the mobile node. MNas the source address 200.2 and as part of an extension header field thehome address of the mobile node 200.3 as well as a field indicating thatthe packet is a binding update 200.4. However, in order to ensure thatthe binding update packet is communicated via the packet data gateway,the mobile node MN is arranged to encapsulate the binding update packet200 using a binding update tunneling header 202, for communicating thebinding update packet 200 via a tunnel 204. The binding update header202 includes an address of the packet data gateway as the destinationaddress 202.1 and the care of address of the mobile node as the sourceaddress 202.2.

After receiving the binding update packet via the tunnel 204, the packetdata gateway 16.7 forwards the recovered binding update packet 200 tothe home agent 10.7 as represented by an arrow 206. As for the previousexamples the packet data gateway 16.7 can be adapted to forward theinternet packets to the home agent 10.7 using either an adaptation ofits routing table, or establishing a dedicated tunnel. It will thereforebe appreciated that both of these examples are possible and so thesehave been represented generically by the arrow 206.

Once the home agent 10.7 has received the care of address CoA of themobile node the internet packets can be forwarded to the mobile nodewithin the visited network by the home agent. For example, if aninternet packet 208 is received by a correspondent node CN then thiswill be forwarded to the home agent because the packet would beaddressed to the home address of the mobile node as the destinationaddress 208.1. Correspondingly the source address will be the address ofthe correspondent node 208.2. Since the home agent 10.7 received thebinding update packet from the packet data gateway 16.7, it will arrangefor all internet packets which are addressed to the mobile node to beforwarded to the packet data gateway 16.7 and as with previous examplesthis can be done by either updating the routing table or by establishinga dedicated tunnel and so this is generally represented by an arrow 210.As with a conventional operation since the data packet 208 is forwardedto the home agent 10.7 using the mobile node's home address HA, the homeagent 10.7 having received the binding update packet 200 will update therelevant address for the mobile node as the care of address CoA so thedata packet 208 will be forwarded to the packet data gateway forcommunicating to the mobile node. Thus as illustrated in FIG. 9 by amobile IP tunnel 212 data packet 208 is encapsulated using a mobile IPheader 216 which has the care of address of the mobile node CoA as thedestination address 216.1 and the address of the packet data gateway asthe source address 216.2. The remainder of the pay load 216.3 containsthe internet data packet 208.

Once the tunneled data packet 214 is received by the mobile node MN thenthe mobile IP header is 216 is removed to provide the received internetpacket 208 at the mobile node MN. Thus far, the example illustrated inFIG. 9 corresponds to the previous examples for mobile IPv4 withappropriate changes being made to reflect the difference between IPv4and IPv6. However, a significant difference between the previousexamples which is provided by the mobile IPv6 is a facility for routeoptimisation provided by the mobile node MN sending a correspondent nodebinding update to a correspondent node CN. A corresponding example forproviding a correspondent node binding update to that shown in FIG. 9 isshown in FIG. 10.

In FIG. 10 the mobile node MN when attached to the visited network VNcommunicates a correspondent binding update packet 220 to thecorrespondent node CN. As shown in FIG. 10 the correspondent bindingupdate 220 has the address of the correspondent node CN as thedestination address 220.1 with the care of address of the mobile nodeCoA as the source address 220.2 and included within a type 2 routingheader field is provided the home address of the mobile node 220.3. Adata field 220.4 provides an appropriate identifier that the internetpacket 220 is a correspondent binding update. As for the example shownin FIG. 9 the correspondent binding update is then tunneled to thepacket data gateway 16.7 by the mobile node MN due to the mobile node MNincluding a pre-set function which causes an internet protocol tunnel204 to be set up between the mobile node MN and the packet data gateway16.7 within the home network HN.

Upon receipt of the correspondent binding update 220 the packet datagateway 16.7 adapts the correspondent binding update to replace the careof address of the mobile node CoA with the address of the packet datagateway as a care of address to form an adapted correspondent bindingupdate packet 224. Thus the packet data gateway replaces the care ofaddress of the mobile node CoA with its own address packet data gatewaywithin the source address field 224.2 with the destination address field224.1 identifying the address of the correspondent node CN.

In addition, the packet data gateway 16.7 also builds a table whichassociates the home address of the mobile node HA which is providedwithin the type 2 routing header field 220.3 within the correspondentbinding update packet 220. The home address of the mobile node HA isassociated with the care of address of the mobile node CoA within adatabase table 226. Thus the mobile nodes home address HA provided inthe extension header field 220.3 serves to provide the packet datagateway 16.7 with an association between the home address HA and thecare of address of the mobile node CoA. Thus by substituting the care ofaddress of the mobile node CoA with its own address PDG the packet datagateway 16.7 forces the correspondent note CN to route all packets whichare to be communicated to the mobile node to go via the packet datagateway. As a result the packet data gateway 16.7 complies with themobile IPv6 standard in performing a route optimisation of thecorrespondent node in accordance with the correspondent node bindingupdate procedure whilst still forcing all internet packets which are tobe communicated to the mobile node within the visited network to go viathe packet data gateway 16.7.

For the example shown in FIG. 10 if the correspondent node wishes tocommunicate a data packet to the mobile node, the correspondent node CNwill use the address of the packet data gateway PDG as the destinationaddress of an internet data packet 230 with the source address being230.2 being that of the correspondent node CN. As for the example shownin FIG. 9 once the packet data gateway receives the internet data packet230 for communication to the mobile node, this packet is tunneled viathe mobile internet protocol tunnel 212 using a tunneling header 232.However, in order to ensure that the internet packet 230 reaches themobile node, the packet data gateway 16.7 replaces the destinationaddress 230.1 with the care of address of the mobile node CoA to form anadapted internet data packet 232. To this end, the internet protocoldata packet sent from the correspondent node CN includes the homeaddress of the mobile node HA in the extension header field 230.3 inaccordance with the mobile IPv6 standard. Thus the packet data gateway16.7, after receiving the internet protocol data packet, detects thehome of address of the mobile node HA in the extension header field anduses the home address of the mobile node HA to retrieve the mobile nodescare of address CoA from the data base table 226. The packet datagateway 16.7 therefore forms the adapted internet data packet 232 byreplacing its own address with the care of address of the mobile node inthe destination address field 232.1. The adapted internet data packetcan then be sent via the mobile IP tunnel 212 using the mobile IP header232 to the mobile node at the mobile nodes care of address.

As with other examples shown above, the mobile internet protocolsecurity tunnel 215 may also be established between the packet datagateway and the mobile node.

Mobile IPv6 Packet Data Gateway in the Visited Network

FIGS. 11 and 12 provide corresponding examples to those of FIGS. 9 and10 but with the packet data gateway within the visited network VN. Asshown in FIG. 11 the mobile node MN is adapted to communicate internetpackets to and from a packet data gateway 16.8 within the visitednetwork VN. As before communication can be effected using either anadaptation of a routing table within the mobile node or establishing adedicated tunnel for internet protocol packets. As for example shown inFIG. 9 following a binding update procedure the mobile node sends abinding update to a home agent 10.8 within its home network HN providingthe home agent 10.8 with a care of address CoA of the mobile node MN. Assuch internet packets received by the home agent from a correspondentnode can be communicated to the mobile node at the care of address CoAwithin the visited network VN. To this end, the home agent 10.8establishes static or dynamic tunnel from the home agent 10.8 to thepacket data gateway 16.8. The received packets at the packet datagateway are then tunneled to the mobile node MN. As for the example ofFIG. 10 once the mobile node has communicated a corresponding bindingupdate to the correspondent node CN, route optimisation can be performedto the effect that packets can be sent directly between thecorrespondent node and the mobile node MN. However, in accordance withthe example shown on FIG. 10 the packet data gateway 16.8 is arranged toreplace the care of address CoA of the mobile node in the correspondentbinding update packet with its own address so that the correspondentnode always sends internet packets directed to the mobile node to thepacket data gateway 16.8 instead. Thus the packet data gateway is“spoofing” a binding update so that the correspondent node CN acts as ifthat the mobile node has a care of address CoA which is the address ofthe packet data gateway 16.8. As for the example shown in FIG. 10 thepacket data gateway uses database table 250 to store an associationbetween the care of address CoA of the mobile node and the home addressof the mobile node HA which is provided within a type 2 routing headerfield of the correspondent binding update received from the mobile node.Thus when the correspondent node communicates an internet data packet252 to the mobile node it uses the address of the packet data gateway16.8 as the destination address 252.1 because the correspondent node nowacts as if the packet data gateway 16.8 is the address of the mobilenode. By providing the home address of the mobile node in accordancewith the mobile IPv6 standard in the type 2 routing header field 252.3,the packet data gateway 16.8 is able to identify the care of address ofthe mobile node CoA and replace its address PDG as a destination addresswith the care of address of the mobile node CoA to forward the internetpacket 252 to the mobile node MN via the tunnel 246.

Various aspects and features of the present invention are defined in theappended claims. Various modifications may be made to the embodimentsherein before described without departing from the scope of the presentinvention. In particular, the present invention is not limited to apacket data network standard or internet protocol version.

1. A telecommunications system operable to provide a mobilecommunications session to a mobile node using an internet protocol,comprising a home packet data network operable to communicate internetpackets to and from the mobile node to provide the communicationssession, when the mobile node is affiliated with the home packet datanetwork, the home packet data network including a home agent of themobile node, and a visited packet data network operable to communicateinternet packets to and from the mobile node to provide thecommunications session, when the mobile node is affiliated with thevisited packet data network, wherein one of the home packet data networkor the visited packet data network includes a packet data gateway forcontrolling the communication of the internet packets to and from thehome packet data network from and to the visited packet data network,and upon receipt of a binding update internet packet providing a care ofaddress of the mobile node following a change of affiliation from thehome packet data network to the visited packet data network, the packetdata gateway and the home agent are operable to establish a route forthe internet packets between the home agent and the mobile node via thepacket data gateway, to the effect that the packet data gateway cancontrol the communication of the internet packets from the home packetdata network to the mobile node and the communication of the internetpackets received from the mobile node via the visited packet datanetwork when the mobile node is affiliated with the visited packet datanetwork.
 2. A telecommunications system as claimed in claim 1, whereinthe packet data gateway is in the home packet data network and uponreceipt of the binding update the packet data gateway is arranged toestablish a mobile internet protocol tunnel for communicating internetpackets to the mobile node in the visited network from the packet datagateway, and upon receipt of the binding update internet protocolpacket, the home agent is arranged to route or to tunnel internetpackets for the mobile node to the packet data gateway.
 3. Atelecommunications system as claimed in claim 2, wherein the packet datagateway establishes an internet protocol security tunnel, between thepacket data gateway and the mobile node, the internet protocol securitytunnel being arranged to be within the mobile internet protocol tunnel.4. A telecommunications system as claimed in claim 3, wherein theinternet protocol security tunnel is an IPsec tunnel in accordance withthe 3GPP standard.
 5. A telecommunications system as claimed in claim 2,wherein the home packet data network is operable in accordance with a3GPP standard and the visited network is operable in accordance with anon-3GPP standard.
 6. A telecommunications system as claimed in claim 2,wherein the packet data gateway establishes an internet protocolsecurity tunnel, between the packet data gateway and the mobile node,the internet protocol security tunnel being arranged to be within themobile internet protocol tunnel.
 7. A telecommunications system asclaimed in claim 2, wherein the visited packet data network includes aforeign agent, the binding update indicating that the mobile node has acare of address assigned by the foreign agent in the visited packet datanetwork, which is sent by the foreign agent to the home agent via thepacket data gateway, and upon receipt of the binding update the packetdata gateway is arranged to establish the mobile internet protocoltunnel between the packet data gateway and the foreign agent, forcommunicating internet packets addressed to the mobile node to theforeign agent for communicating to the mobile node in the visited packetdata network at the care of address.
 8. A telecommunications system asclaimed in claim 1, wherein the visited packet data network includes aforeign agent, the binding update indicating that the mobile node has acare of address assigned by the foreign agent in the visited packet datanetwork, which is sent by the foreign agent to the home agent via thepacket data gateway, and upon receipt of the binding update the packetdata gateway is arranged to establish the mobile internet protocoltunnel between the packet data gateway and the foreign agent, forcommunicating internet packets addressed to the mobile node to theforeign agent for communicating to the mobile node in the visited packetdata network at the care of address.
 9. A telecommunications system asclaimed in claim 8, wherein after the packet data gateway hasestablished the internet protocol tunnel between the packet data gatewayand the foreign agent, the packet data gateway is operable to establishan internet protocol security tunnel between the packet data gateway andthe mobile node via the foreign agent, the internet packets for themobile node being arranged to pass through the internet protocolsecurity tunnel, by inserting an internet security tunnel header betweena mobile internet protocol header for the mobile internet protocoltunnel and the internet packet addressed to the mobile node at the careof address, the internet security tunnel header having a destinationaddress of the care of address of the mobile node and an address of thepacket data gateway as a source address.
 10. A telecommunications systemas claimed in claim 9, wherein the internet protocol security tunnel isan IPsec tunnel in accordance with the 3GPP standard.
 11. Atelecommunications system as claimed in claim 1, wherein the packet datagateway is in the visited packet data network and the mobile node isarranged to communicate the internet packets to the packet data gatewayin the visited packet data network, when the mobile node is affiliatedwith the visited packet data network, to generate a care-of-address, toform a binding update packet for communication to the home agent in thehome packet data network, and to communicate the binding update packetfor the home agent to the packet data gateway, and the packet datagateway is arranged upon receipt of the binding update, to establish abinding update internet protocol tunnel between the packet data gatewayand the home agent for communicating the binding update internetprotocol packets to the home agent, and upon receipt of the bindingupdate, the home agent is arranged to establish a mobile internetprotocol tunnel between the home agent and the packet data gateway forcommunicating the internet packets for the mobile node on the visitedpacket data network.
 12. A telecommunications system as claimed in claim11, wherein the home packet data network is operable in accordance witha non-3GPP standard and the visited network is operable in accordancewith a 3GPP standard.
 13. A telecommunications system as claimed inclaim 11, wherein the internet protocol is internet protocol version six(IPv6).
 14. A telecommunications system as claimed in claim 1, whereinthe visited packet data network includes the packet data gateway and aforeign agent, the foreign agent being operable to generate acare-of-address for the mobile node within the visited packet datanetwork, when the mobile node is affiliated with the visited packet datanetwork, to form a binding update packet for communication to the homeagent in the home packet data network, and to communicate the bindingupdate packet for the home agent to the packet data gateway, and thepacket data gateway is arranged upon receipt of the binding updateinternet protocol packet, to establish a binding update tunnel from thepacket data gateway in the visited packet data network to the home agentin the home packet data network, and to communicate the binding updateinternet protocol packet to the home agent in the home packet datanetwork, via the internet protocol tunnel.
 15. A telecommunicationssystem as claimed in claim 14, wherein upon receipt of the bindingupdate internet protocol packet the home agent in the home packet datanetwork is arranged to establish an internet protocol tunnel forcommunicating internet packets from the home agent in the home network,for the mobile node at the care-of-address, to the packet data gatewayin the visited network, and the packet data gateway is arranged tocommunicate the internet packets for the mobile node at thecare-of-address to the foreign agent, the foreign agent being arrangedto communicate the internet protocol packets to the mobile node.
 16. Atelecommunications system as claimed in claim 15, wherein the packetdata gateway is arranged to communicate internet packets for the mobilenode to the foreign agent using one of an update of a routing tableidentifying a next address to which internet packets for the mobile nodeare to be sent, the next address being that of the foreign agent or afurther internet protocol tunnel, between the packet data gateway andthe foreign agent.
 17. A telecommunications system as claimed in claim1, wherein the internet protocol is internet protocol version four(IPv4).
 18. A telecommunications system as claimed in claim 1, whereinthe internet protocol is internet protocol version six (IPv6).
 19. Amethod of providing a mobile communications session to a mobile nodeusing an internet protocol, the method comprising communicating internetpackets to and from the mobile node to provide the communicationssession, when the mobile node is affiliated with a home packet datanetwork, the home packet data network including a home agent of themobile node, communicating the internet packets to and from the mobilenode to provide the communications session, when the mobile node isaffiliated with a visited packet data network, and controlling thecommunication of the internet packets to and from the home packet datanetwork from and to the visited packet data network using a packet datagateway, wherein the communicating the internet packets to and from themobile node to provide the communications session, when the mobile nodeis affiliated with a visited packet data network, includes generating abinding update internet protocol data packet providing a care-of-addressof the mobile node following a change of affiliation from the homepacket data network to the visited packet data network, communicatingthe binding update internet protocol data packet to the home agentwithin the home packet data network via the packet data gateway, andupon receipt of the binding update internet protocol packet establishinga route for the internet packets to be communicated between the homeagent and the mobile node via the packet data gateway.
 20. An apparatusfor providing a mobile communications session to a mobile node using aninternet protocol, the apparatus comprising means for communicatinginternet packets to and from the mobile node to provide thecommunications session, when the mobile node is affiliated with a homepacket data network, the home packet data network including a home agentof the mobile node, means for communicating the internet packets to andfrom the mobile node to provide the communications session, when themobile node is affiliated with a visited packet data network, and meansfor controlling the communication of the internet packets to and fromthe home packet data network from and to the visited packet data networkusing a packet data gateway, wherein the communicating the internetpackets to and from the mobile node to provide the communicationssession, when the mobile node is affiliated with a visited packet datanetwork, includes means for generating a binding update internetprotocol data packet providing a care-of-address of the mobile nodefollowing a change of affiliation from the home packet data network tothe visited packet data network, means for communicating the bindingupdate internet protocol data packet to the home agent within the homepacket data network via the packet data gateway, and means for uponreceipt of the binding update internet protocol packet establishing aroute for the internet packets to be communicated between the home agentand the mobile node via the packet data gateway.